The question is not if but when southern California will be hit by a major earthquake— one so damaging that it will permanently change lives and livelihoods in the region. How severe the changes will be depends on the actions that individuals, schools, businesses, organizations, communities, and governments take to get ready. To help prepare for this event, scientists of the U.S. Geological Survey (USGS) have changed the way that earthquake scenarios are done, uniting a multidisciplinary team that spans an unprecedented number of specialties. The team includes the California Geological Survey, Southern California Earthquake Center, and nearly 200 other partners in government, academia, emergency response, and industry, working to understand the long-term impacts of an enormous earthquake on the complicated social and economic interactions that sustain southern California society. This project, the ShakeOut Scenario, has applied the best current scientific understanding to identify what can be done now to avoid an earthquake catastrophe.

The Scenario outlines a hypothetical earthquake in which:

The strongest shaking and greatest damage is near the stretch of the San Andreas Fault that extends through the fastest growing areas of Southern California, including the Coachella Valley, Inland Empire and Antelope Valley.

At least 10 million people will be in the heavily shaken areas. California's efforts at mitigation have concentrated on life safety and have been successful. Thus, in spite of the large numbers of people in highly shaken areas, deaths are estimated at only 1,800.

Building types known to be vulnerable to damage and collapse, do indeed sustain major damage. All un-reinforced masonry buildings within 15 miles of the San Andreas Fault are completely destroyed. Those that are not retrofitted kill many occupants. Many other older building types without retrofitting contribute to over $33 billion in damage to buildings.

The fault offsets all lifelines crossing into Southern California at Cajon Pass (Interstate 15), San Gorgonio Pass (Interstate 10) and along Route 14, including pipelines, power lines, roads, railways, telecommunications and aqueducts.

Strong shaking continues in downtown Los Angeles for 55 seconds – nearly 8 times longer than in the Northridge Earthquake

The prolonged, strong shaking heavily damages and sometimes collapses hundreds of old brick buildings, hundreds of older commercial and industrial concrete buildings, many wood-frame buildings, and even a few, high-rise steel buildings. The building damage causes tens of thousands of injuries and hundreds of deaths, and leaves many thousands of people without homes or jobs.

Fire doubles the fatalities and economic losses. Around Southern California, there will be 1,600 fires started large enough to warrant a 911 call, and some fires merge into conflagrations that burn hundreds of city blocks. Assuming no Santa Ana winds, the models still indicate a further $65 billion in direct losses from the fires.

Nearly two thirds of the hospital buildings are non-functional in Los Angeles, Orange, Riverside, and San Bernardino counties.At the same time, 50,000 people will seek treatment at emergency rooms.

Thanks to a $6 billion investment in seismic safety, the state highway system fares well. However, although collapse is avoided, some bridges are non-functional so that much of the highway is not passable on the day of the event. The long duration of shaking takes a greater toll on bridges and overpasses under the jurisdiction of cities and counties, where the retrofitting process is not completed or not yet begun.

The largest long-term economic disruption comes from damage to our water distribution system. The damage to this system will be so extensive that some areas will just have to replace the whole system and some buildings will be without water for as much as 6 months. The business interruption costs from the lack of water will be $50 Billion.

Most of the damage is predictable and much is preventable. Individuals can protect themselves and help their community by:- Storing more water than they already have- Keeping a fire extinguisher and knowing how to use it.- Securing their space. This means securing building contents from flying around and reinforcing a building they own to the most current standards.

“The planned emergency drill is underpinned by the most comprehensive analysis ever of what a major Southern California earthquake would mean on the ground,” said Dr. Lucile Jones, chief scientist for U.S. Geological Survey’s Southern California Multi-Hazards Demonstration Project. “We know this science will help state and local agencies develop comprehensive emergency-response plans that will help us avoid the worst impacts of a major quake.”

The ShakeOut Earthquake Scenario - A Story That Southern Californians Are Writing, USGS Circular 1324/CGS Special Report 207 - "More effectively than any statistics, this narrative describes what this magnitude 7.8 earthquake would be like in southern California if no additional actions are taken for mitigation or preparedness." Click here to download Special Report 207.

The ShakeOut Scenario - Effects of a Potential M7.8 Earthquake on the San Andreas fault in Southern California, CGS Preliminary Report 25/USGS Open File Report 2008-1150 - This PDF is the full preliminary report for the 2008 ShakeOut Scenario. The PDF is around 21 megabytes. Click here to download Preliminary Report 25.

Listed below are the 10 Appendices that accompany CGS Preliminary Report 25/USGS Open File Report 2008-1150. (Click on each appendix to download)

California Geological Survey Earthquake Scenario Web Page - CGS has published nine earthquake scenarios in the past 26 years for major faults throughout the state. The reports examine the possible destruction that could be caused from large earthquakes along these faults. Click here for the Scenarios Page.